1. Field of the Invention
The present invention relates to a method of manufacturing a CMOS image sensor. More particularly, the present invention relates to a method of manufacturing a CMOS image sensor which is capable of preventing the metal pad of a semiconductor device from corroding due to any residual material, such as a development solution, from the colored photoresist film process.
2. Discussion of the Related Art
In a color image sensor, color filters are arrayed on a photosensitive portion so as to receive external light, generate and store photocharges. A color filter array (CFA) is formed of three colors of red, green and blue or three colors of yellow, magenta and cyan.
An image sensor includes a photosensitive portion for sensing light and a logic circuit portion for converting the sensed light into an electrical signal so as to generate data. In order to increase photosensitivity, it has been attempted to increase the size of the photosensitive portion, however, since the logic circuit portion cannot be removed, this attempt has restricted due to the size constraints of the image sensor. Accordingly, in order to increase the photosensitivity, light-focusing technology is used to change the paths of any light beams which are directed regions outside photosensitive region so that the light beams are redirected to the area of the photosensitive portion. Typically, such light-focusing technology operates by forming micro lenses on the color filters.
A method of forming an image sensor known in the art typically comprises forming a field insulating film for electrical insulation between devices on a silicon substrate. Next, unit pixels including photosensitive regions of light-receiving elements are formed, followed by a metal interlayer insulating film, and a plurality of metal wiring.
In order to protect the device from being exposed to water or scratching, an oxide film and a nitride film are sequentially coated over the device so as to form a protective film, wherein the protective film is etched so as to form an area capable of forming an electrical connection with the device during the wire bonding process. Typically, this comprises forming a metal pad opening portion for exposing a portion of the metal pad. Later, a color filter array is formed such that the image sensor can capture a color image.
However, residual materials, such as development solution or the like, which are used during the photoresist film process may reach the exposed surface of the metal pad, causing corrosion, damage or contamination in the metal pad.